The present disclosure relates to systems and methods for removing anions from waste water.
Mining involves the excavation of ore and generates waste material through ore beneficiation or “stripping” to access the valuable ore. The exposure of the waste materials to the environment can result in mine-affected water. Typical concentrations of waste materials in mine affected water are provided Table 1 below:
TABLE 1Content Content Content Ion(ppm)Ion(ppm)Ion(ppm)Ca+2466K+12.1NO3−1215Mg+2248Cd+20.001Cl−17.2Ba+20.11Se+60.42F−13.8Na+17.6SO4−21535HCO3−1521
The presence of anions such as selenate (SeO42−), sulfate (SO42−), nitrate (NO31−), and other anions in the waste water may limit discharge. In particular, the selenate and nitrate levels in water discharge are often tightly controlled (e.g., to a selenium level 10 ppb and a nitrate level ≤13 ppm without conversion to ammonium or nitrite).
There are many technologies for treating wastewater. However, the cost of treatment is often high (both capital and operating cost). In addition, the treatment of waste water is sometimes so complex that it is technologically advantageous to set up a treatment “train” or series of technologies to reach the ultimate goal of waste water treatment. For example, where nitrate and selenate ions are both to be removed from a sulfate solution, it may be advantageous to use one process for nitrate ion removal followed by a second process for selenate removal. This may be beneficial if the nitrate ions interfered with the efficient removal of selenate ions from the waste water. It would be desirable to provide cost-effective methods for removing various ions from mine-affected water, primarily selenate, sulfate, and nitrate, but being applicable to other anions depending on the anion content of the water.